Mossbauer Spectroscopy


Relevance


     Mössbauer Spectroscopy is a spectroscopic method based on the recoil-free, resonant absorption and emission of low energy gamma rays (Mössbauer effect) in solids. The method allows us the study of hyperfine interactions in solids containing 'Mössbauer elements' e.g. Fe, Sn, Eu etc. The detection limit of this method is ~ 10-8 eV. Based on the hyperfine parameters obtained from Mossbauer spectra one can obtain useful information in different scientific fields. In the following a couple of successful applications are highlighted:

  • valence state, electronegativity, ligand effects, chemical kinetics, corrosion, catalysis;
  • magnetization states, superparamagntic effects, local environment, structure and the relative phase ratio;
  • phase transitions studies
  • understanding the structure and function of iron containing enzymes and bio materials;
  • amorphous and nano material's study
  • physical metallurgy, monitoring and the optimization process of alloys and special steels preparation;
  • geology for identifying the composition of iron- containing specimens including meteorites, Moon and Mars planet rocks;
  • cosmology (gravitational red shift, second-order transverse Doppler effect predicted by the theory of relativity), due to the very high energy resolution, etc.;
  • Study of surfaces (0-300 nm) by means of the conversion electron detection (CEMS).
Mössbauer spectrometer with cryostat operating in presence of magnetic fields at ultra-low temperatures

Mössbauer spectrometer with cryostat operating in presence of magnetic fields at ultra-low temperatures

The system consists in two main parts :


· A. ICEoxford (England) cryogenic low temperature superconducting magnet system for Mössbauer measurements;

· B. WissEL (Germany) Mössbauer spectrometer;


   Cryogenic low temperature superconducting magnet system for Mössbauer measurements provide a magnetic field at the sample up to 6 Tesla with vertical field direction (perpendicular on gamma rays direction) and a homogeneity of the magnetic field better than +/-1% in a 10 mm dsv.
    The sample temperature can be varied in the range of 1.4 to 300K. The system includes temperature controller, superconducting power supply, pump and lines for operating the temperature insert, helium level meter, helium storage vessel, turbo molecular pump.
    The Mössbauer spectrometer (WissEl-Germany) consists in two components: an electro-mechanic system which create the conditions for the resonant absorption of gamma rays in the sample and the system for the detection and acquisition of gamma rays, emitted by the radioactive source, after crossing the sample under study.
   The first component contains the velocity transducer and the drive unit and moves the radioactive source with velocity up to ±300 mm/s with linearity better than 0.15 % up to ± 100 mm/s. In constant acceleration mode, the velocity waveforms SINE or TRIANGLE can be optionally selected.
   The second component, for the detection and data acquisition is a NIM standard and contains the following devices: proportional counter, preamplifier and amplifier, high-voltage supply, NIM BIN with power supply and MCS/PHA card for data acquisition.

Mössbauer Spectrometers Models AME-20  and AME-50

Mössbauer Spectrometers Models AME-20 and AME-50

Mössbauer Spectrometer Model AME-20


The parts of the system :

· Linear Velocity transducer MVT-2;

· Transducer Driving unit MD-2;

· MS Windows PC with with inserted card as function generator and acquisition data sawtooth wave form velocity, maximum velocity range: +/- 300 mm/s, integral linearity: 1% up to +/- 30 mm/s

· Gamma-ray Spectrometer in NIM system with Ortec modules, Harshaw charge sensitive preamplifier and IFIN Gas Proportional Counter for low energy


Accessories for sample temperature variation


· Liquid Nitrogen Cryofurnace MC-3, temperature range 80 to 4000K;

· Furnace MF-2A, temperature range 300 to 10000K;

· Temperature controller MTC-3 for cryofurnace and furnace, temperature stability of ± 0.4 K


Mössbauer Spectrometer Model AME-50


System components :

· Linear Velocity transducer MVT-3;

· Transducer Driving unit MDF-N-5;

· Function Generator MFG-N-5 triangle and sawtooth wave form velocity, maximum velocity range: +/- 600 mm/s, integral linearity: 0.1% up to +/- 10 mm/s;

· MS Windows PC with MCS/PHA CMCA-550 module as function generator and acquisition data;

· Gamma-ray Spectrometer in NIM system with Ortec modules, Harshaw charge sensitive preamplifier and LND Gas Proportional Counter;

Advanced Mössbauer Spectroscopic System MS4/CCR4K

Advanced Mössbauer Spectroscopic System MS4/CCR4K

System components :


· Gamma sources for Mössbauer isotopes 57Fe and 119Sn ;

· W302 Resonant Gamma-ray Spectrometer with VT400 Linear Velocity Transducer, triangle wave form velocity, maximum velocity range: +/- 100 mm/s, integral linearity: 0.1% up to +/- 20 mm/s ;

· W202 Gamma-ray Spectrometer with Kr Gas Proportional Counter W202 Gamma-ray Spectrometer is a compact, highly integrated system providing both pulse-height analysis and dual single-channel analysis ;

· MS Windows PC with USB interface The MS4 software installed on the PC includes the W202 control program, the W302 control program and the WMOSS Mössbauer spectral analysis software. ;

· CCR4K closed cycle Special Mössbauer refrigerator system;

· W106 Dual Channel Temperature Controller;

· VF 100 Vacuum Furnace;

     The Advanced Mössbauer Spectroscopic System MS4/CCR4K is a complete equipment to obtain a variable temperature for sample in the temperature range: 4.5 ÷ 1000 K with a stability of ± 0.2 K: 4.5 ÷ 300 K with CCR4K Special Mössbauer refrigerator system, 300 ÷ 1000 K with VF 100 Vacuum Furnace.

Versatile flow-gas proportional counter (lateral view).

Versatile flow-gas proportional counter (lateral view).

Accessories for backscattering measurements


     Gas-flow proportional detectors for the detection of conversion electrons or characteristic X-ray, in backscattering geometry, were made in laboratory. Actually we are able to perform measurements on the following Mössbauer isotops: 57Fe, 119Sn and 151Eu.

Main characteristics :


· Outer dimensions: height 61 to 98 mm, width: 80 mm diameter;

· Detection volume can be changed in large limits: diameter 40 mm; height 1 to 38 mm at a diameter of 40mm;

· Maximum diameter of the sample: 21 mm;

· Flow gas: 94% He + 6% CH4 or 99% He + 1% C4H10;

· Flow gas rate: 50 to 1000 cm3/hour;

· High voltage: 700 to 1100 V;

· Sample holder allows simultaneously surface and transmission;

· It is possible to make also measurements by X-ray or gamma ray with this detector;

DIAMANDESCU Lucian Senior Researcher I
Ph.D. Supervisor
Personal Page
FEDER Marcel Senior Researcher II Personal Page
POPESCU Traian Researcher III Personal Page
VLAICU Aurel-Mihai Researcher III -
STERIAN Gheorghe Sub-Engineer Personal Page

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Laboratory of Atomic Structures and Defects in Advanced Materials